Forest edge influence on tree sapling drought damage in Northern Bavaria

Climate change is expected to increase the frequency of extreme weather events like heat waves and droughts in Central Europe. Drought-induced tree mortality determines the future vitality, structure and functioning of forests. To better predict the arising changes in forest dynamics and identify adaptation strategies, more information on the mechanisms driving observed forest die-back patterns is needed. Recruitment processes and sapling growth are of special importance for future forest composition, but few field studies exist on the response of saplings to drought. In a fragmented forest landscape, as it is dominant in Germany, considering forest edge effects adds a relevant perspective to forest-related drought research. This study investigates the influence of forest edge distance on drought damage in deciduous tree saplings during the hot and dry year 2018. Based on field measurements of leaf discoloration of 2108 saplings out of 214 plots located in Northern Bavaria, effects of edge distance and edge orientation on sapling vitality were assessed. Species were categorised as either “interior” or “edge” species according to selected traits, in order to analyse differences of drought response between species groups. The results indicate more pronounced drought damage in saplings growing in a 20 m wide edge zone. Saplings classified as “interior species” showed a higher vitality throughout all edge distance categories but experienced almost the same level of drought damage as “edge species” in the 20 m edge zone. An effect of edge orientation on sapling vitality was not found. These findings highlight the need of further knowledge on the relationship between tree vitality and edge characteristics to develop forest edge management strategies that enhance forest resilience under climate change.